AskDefine | Define ohm

Dictionary Definition



1 a unit of electrical resistance equal to the resistance between two points on a conductor when a potential difference of one volt between them produces a current of one ampere
2 German physicist who formulated Ohm's Law (1787-1854) [syn: Georg Simon Ohm]

User Contributed Dictionary



Named after the German physicist Georg Ohm.



  1. In the International System of Units, the derived unit of electrical resistance; the electrical resistance of a device across which a potential difference of one volt causes a current of one ampere. Symbol: Ω


the derived unit of electrical resistance



ohm , (plural: ohms, diminutive: ohmpje, plural diminutive: ohmpjes)
  1. ohm

Usage notes

The plural is not actually used. A resistance is actually expressed as De weerstand bedraagt 56 ohm.




  1. ohm

Extensive Definition

The ohm (symbol: Ω) is the SI unit of electrical impedance or, in the direct current case, electrical resistance, named after Georg Ohm.


The ohm is the electric resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force.
\Omega = \dfrac = \dfrac


  • A measurement in ohms is the reciprocal of a measurement in siemens, the SI unit of electrical conductance. Note that 'siemens' is both singular and plural. The non-SI unit, the mho (ohm written backwards), is equivalent to siemens but is mostly obsolete and rarely used.
  • Ohms to watts: The power dissipated by a resistor may be calculated using resistance and voltage. The formula is a combination of Ohm's law and Joule's law:
where P is the power in watts, R is the resistance in ohms and V is the voltage across the resistor.
This method is not reliable for determining the power of an incandescent light bulb, resistance heater or electric short since all these devices operate at high temperatures and the resistance measured using a meter will not represent the operating resistance. For these conditions instead multiply V by current in amperes to get power in watts.

References and notes

ohm in Arabic: أوم
ohm in Asturian: Ohmiu
ohm in Bosnian: Om
ohm in Breton: Ohm
ohm in Bulgarian: Ом
ohm in Catalan: Ohm
ohm in Czech: Ohm
ohm in Danish: Ohm
ohm in German: Ohm
ohm in Modern Greek (1453-): Ωμ (μονάδα μέτρησης)
ohm in Spanish: Ohmio
ohm in Esperanto: Omo
ohm in Basque: Ohm
ohm in Persian: اهم
ohm in French: Ohm (unité)
ohm in Galician: Ohm
ohm in Korean: 옴 (단위)
ohm in Hindi: ओह्म
ohm in Croatian: Om
ohm in Indonesian: Ohm
ohm in Icelandic: Óm
ohm in Italian: Ohm
ohm in Hebrew: אוהם
ohm in Latvian: Oms
ohm in Dutch: Ohm (eenheid)
ohm in Japanese: オーム
ohm in Norwegian: Ohm
ohm in Norwegian Nynorsk: Ohm
ohm in Polish: Om (jednostka)
ohm in Portuguese: Ohm
ohm in Romanian: Ohm
ohm in Russian: Ом
ohm in Slovak: Ohm (jednotka)
ohm in Slovenian: Om
ohm in Serbian: Ом (јединица)
ohm in Finnish: Ohmi
ohm in Swedish: Ohm
ohm in Thai: โอห์ม
ohm in Vietnamese: Ohm
ohm in Turkish: Ohm
ohm in Ukrainian: Ом
ohm in Chinese: 歐姆
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